The design of efficient fuel systems requires the prediction of the air entrainment flow rate from the atmosphere into the fuel tank and clarification of the changes in the state of the mixed gas consisting of air and fuel evaporative gas (vapor) within the fuel tank. The air entrainment flow rate was predicted in a previous study. This study focused on the vapor newly generated by the entrained air and developed a formula to predict the corresponding quantity of vapor displaced into a canister during refueling in the initial design phase of a fuel tank system for automobiles. The displaced mixed gas comprises the gas pushed out by the supplied fuel and entrained air and that pushed out by the vapor generated by the entrained air. The state changes of the mixed gas within the fuel tank and its displacement process were modeled. Subsequently, the fundamental formula for the vapor displacement quantity was derived by applying the gas state equation and law of partial pressure. It was further developed to consider the effect of the recirculation line, which reduces the air entrainment flow rate, and changes in the physical properties of the vapor owing to temperature variations in the residual fuel. Finally, the vapor displacement quantity was calculated for actual vehicles by using the derived prediction formula and the results were compared with measurement results. The predictions showed good agreement with the measured values, confirming the applicability of the formula to the prediction of the quantity of vapor displacement.

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We studied the traffic flow management on highway main line to assist drivers in merging using CACC (Cooperative Adaptive Cruise Control) vehicles which can adjust vehicle speed and time-headway based on control target from out-car via wide-area or narrow-area communication. By conducting platoon simulations to clarify the effect of CACC control on traffic flow under various vehicle and driver types by combining control target (speed or time-headway) and control trigger (time or position), we found that speed management based on narrow area communication (i.e., position triggering) is most effective to manage the traffic flow before and after merging sections in a quick and stable manner even at relatively low CACC ratio. The study also revealed the problems that the time-headway adjustment results in excessive speed changes and that time triggered speed management can cause irregular speed fluctuations. These findings are useful in providing driving assistance by controlling traffic flow stably, and we will realize desirable merging assistance to drivers in the future.

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